Terragrim

Type	Weapon
Damage	17 (Melee)
Knockback	3 (Very weak)
Critical chance	4%
Use time	25 (Fast)
Velocity	15
Tooltip	Unleashes a dicing flurry
Rarity
Buy	25 GC
Sell	5 GC
Research	1 required
Use	https://terraria.wiki.gg/wiki/File:Item_1.wav

Desktop/Console/Mobile-Only Content: This information applies only to the Desktop, Console, and Mobile versions of Terraria.

The Terragrim is a rare pre-Hardmode melee weapon that appears to be a sword, but does not present an actual blade when used. Instead of an overhead broadsword swing or a shortsword stab, the Terragrim autoswings and appears as a series of blurred green slashes aimed in the direction of the cursor. Anything within this area takes constant damage at a rate far exceeding the weapon's stated use time. This damaging area has a rather wide spread, even attacking behind the player for a very short distance.

Sword in Stone
Background Objects

A junk (left) and enchanted (right) sword in stone. Only the right one has a chance to drop the Terragrim.

It is obtainable from the unique background object found in an Enchanted Sword Shrine or very rarely in the Caverns layer. When the object is destroyed, it has a 1/50 (2%) chance to drop a Terragrim rather than an Enchanted Sword.

The Arkhalis is the Terragrim's Hardmode, Expert-exclusive upgrade.

Its best modifier is Godly or Demonic. Both modifiers increase the average damage output by the same amount. The Terragrim's unique means of attack is unaffected by any size and speed modifiers.

The Terragrim attacking Target Dummies.

Notes

In Celebrationmk10 and Get fixed boi worlds, the Terragrim can be purchased from the Princess during a Blood Moon for 25 GC.

Tips

Its speed makes it very easy to defeat the Brain of Cthulhu's second phase, allowing the user to stand still and avoid taking damage.
The best world size for finding the Terragrim is medium, due to there being 1-2 Enchanted Sword Shrine in small worlds, 1-3 in medium worlds, and 2-4 in large worlds, with each shrine having a 50% chance to actually generate. Despite there usually being more Enchanted Sword Shrines in large worlds, it is easier to find them in medium worlds due to there being less space in between each shrine.
Since the presence of the Terragrim is determined when the background object is destroyed, it is possible to force its appearance by "save scumming": Having found an Enchanted Sword Shrine with an enchanted sword in stone, switch autosave off, and then keep breaking the background object and force-quitting Terraria (not pressing "Save and Exit" in the pause menu, but closing the Terraria application itself) until obtaining a Terragrim instead of an Enchanted Sword. While this method may be considered cheating by many, it can be useful for some players.

Trivia

The Terragrim's name is a reference to the Crissaegrim, also known as Valmanway, from the platform-adventure action role-playing game Castlevania: Symphony of the Night. Like the Arkhalis, the Terragrim's function and appearance are also based off of the Valmanway.
The Terragrim appears in the Zenith's animation despite it not being used to craft the Zenith.
The Terragrim replaced the Arkhalis as a special weapon found in Enchanted Sword Shrines, as the Arkhalis is found in Arkhalis's developer set as of 1.4.0.1.
Even if using an inventory editor to obtain the Legendary modifier, it will not change how fast the sword slashes or how large the slashes are.